1. Field of the Invention
The present invention is related to bicycle transmissions. More specifically, the present invention relates to a system and method for mounting a bottom bracket bicycle planetary gear apparatus.
2. Description of the Related Art
The prior art discusses generating an overdrive condition by blocking a sun gear, inputting driving forces to the planet carrier and outputting through a ring gear at a rotational speed greater than the input speed. This is the overdrive condition.
The one to one or non overdrive condition is generated by locking either the sun gear or ring gear to the planet carrier so that the gearing rotates en-masse. In the overdrive condition, when the sun gear is blocked or prevented from rotating relative to the bike frame, a system for transferring the blocking torque from the sun gear to a control mechanism and from the control mechanism to the bike frame is required.
Various systems have been used to secure the control mechanism to the bike frame in devices which are known to the inventor. For example a torque arm can be secured to a frame member such as a chain stay by means of a strap. This system has been used by the Schlumpf “Speed Drive” and “Mountain Drive” bottom bracket planetary systems. The control mechanism can also be secured to the frame by means of brazeon tabs added to the bottom bracket shell for the purpose of mounting such things as chain guards. Such brazeon tabs may not have been added to the bike frame with the precision required for cooperation with a planetary control mechanism. In these cases, the brazeons and bottom bracket shell may require additional machining to bring them into correct relationship to the planetary control mechanism. For example, the Sram “Hammerschmidt” bottom bracket planetary system advises the customer to study an installation manual more than sixty pages long before attempting to install a Hammerschmidt to an unprepared bike frame. According to the installation manual, some frames may not be suitable for the application because the brazeon tabs, called ISCG (International Standard Chain Guard) tabs may not be located in the precise locations required by the Sram Hammerschmidt.
In general it is preferable to mount a bottom bracket planetary system to a standard bike frame with no special modifications or added brazeon tabs.